144 THE SPINAL CORD AND CEREBELLUM 



shown that the will, as we frequently use the term, 

 must consist of two very different elements, viz., a 

 sensory element, which may take the form of sensa- 

 tion of a primary kind, or may be so complicated as 

 to represent an idea or group of sensations, but which 

 in all cases of conscious action is connected with — nay, 

 is generated in — the cerebral cortex, and in addition 

 to this an element by means of which sensation and 

 nutrition — that is to say, chemical action — are both 

 The cere- intensified. The seat of this second element is 



bellum m 



voluntary generally supposed to be the cerebral cortex also, and 

 this has so happened because we are always apt to 

 connect will with consciousness. But natural as this 

 connection may be, it by no means implies com- 

 munity of origin ; and a histological examination of 

 the cortex reveals the presence of no cells (if we 

 exclude motor cells), to which, as in the case of the 

 cerebellar cells of Purkinje, we should be justified, by 

 reason of their size and relations, in attributing a 

 power to increase the impulse of other cells. And 

 since, moreover, vaso-motor changes are an essential 

 accompaniment of all forms of activity throughout 

 the body, we should expect to find a more or less 

 close relationship between the ' increase of impulse ' 

 cells and the vaso-motor mechanism, and that this 

 does really exist seems the more probable owing to 

 the proximity and relation of the cerebellum to the 

 medulla oblongata, the seat of the chief vaso-motor 

 centre. A curious feature of the cerebellum is the 

 colouration of the rust-coloured layer. Is this due to 



